Anaplasma platys (former Ehrlichia platys) causes canine cyclic thrombocytopenia in tropical and warm regions of the world, like the Mediterranean, Asia, Middle East, Africa, Australia, and the USA. Canine anaplasmosis is a widespread disease and therefore called a “canine emerging disease”. The Brown Dog tick (Rhipicephalus sanguineus) and Dermacentor spp. are thought to transmit the pathogen. Anaplasma platys are the only rickettsia known to infect platelets. The organisms appear as round, oval or bean shaped blue cell inclusions in platelets and range from 0.35 to 1.25 μm in diameter.
Signs of Anaplasma platys infection include fever, anorexia, lethargy, primary hemostatic disorders as the pathogen destroys platelet cells of the host, mild anemia, and lymphadenomegaly. Bacteraemia and subsequent thrombocytopenic episodes (with platelet counts below 20,000/μl) recur at 1 to 2 week intervals. Co-infection with E. canis may lead to severe diseases.
Generally, the methods employed for Anaplasma platys diagnosis includes blood smear, serologic diagnosis and molecular diagnosis, but each method has some limitations.
A diagnosis of Anaplasma platys may be made by detecting organisms within platelets on stained blood films or buffy coat smears (e.g. Giemsa or Diff-Quik). Due to cyclic parasitemia the pathogen could either be absent or present in very low numbers. Thus this method is not reliable, and shows low sensitivity and time consuming.
Serologic diagnosis may be helpful in identifying the presence of antibodies to Anaplasma platys, but may not detect early infections during the acute phase of disease. The limitation of serologic diagnosis is cross-reaction, and the cross-reaction among the Ehrlichia spp. and Anaplasma spp. is commonly recognized. Moreover, it is difficult to differentiate between post exposure and present infection.
The most current and best way to diagnose Anaplasma platys is molecular diagnosis, especially by polymerase chain reaction (PCR) testing. PCR, which is more sensitive and specific technique, offers an alternative approach for the diagnosis of anaplasmosis. An 16S rRNA gene sequence has been helpful in identifying species of Anaplasma. For example, the VetPCR A. platys Detection Kit provided by BioinGentech is used to diagnose Anaplasma platys infection, and it is a very fast, accurate and reliable technique. However, end-point PCR detection method, i.e. gel electrophoresis, should be combined with this diagnostic kit, and the whole procedure will take 3 hours, which is quite labor and time consuming.
Therefore, there is a need of providing an Anaplasma platys diagnosis in order to overcome the above drawbacks.